A silicon carbide (SiC) has an excellent physical property such that a band gap is triple, a breakdown electric field intensity is about tenfold and a thermal conductivity is about triple, in comparison with a silicon (Si). It is possible to realize a semiconductor device which has a low loss and is excellent in a high temperature operation, by using a characteristic of the SiC mentioned above.
In the semiconductor device using the SiC, in order to improve an electron transfer degree of an inversion layer and improve a reliability of a gate insulating film, it has been known to use a silicon dioxide (SiO2) added a nitrogen (N) as the gate insulating film.
In the semiconductor device using the SiC mentioned above, it is important to adjust a threshold value of a gate voltage without deteriorating a current and voltage property.